The present invention relates to a microplasma current switch thereof; and, more particularly, to a microplasma current switch thereof enabling to increase the amount of electric current passing through the microplasma current switch by adjusting the areas of electrodes exposed to plasmas and enabling to maximize the area of an electrical device by optimizing the structure of electrodes.
As information telecommunication technologies have been greatly developed, a variety of demands for electronic display devices are highly increased to keep up with the developing information society. And, so do the demands for various displays. In order to satisfy the demands of the information society, for electronic display devices are required characteristics such as high-resolution, large-size, low-cost, high-performance, light-weight, slim-dimension, and the like, for which new flat panel displays (FPDs) are developed as a substitution for conventional cathode ray tubes (CRTs).
The FPDs include LCDs (liquid crystal displays), ELDs (electroluminescent displays), PDPs (plasma display panels), FEDs (field emission displays), VFDs (vacuum fluorescence displays), LEDs (light emitting displays), and the like. Compared with a non-emissive device such as LCDs, ELDs attract attention as a FPD having a response speed faster than that of the non-emissive display, excellent brightness by self-luminescence, easy fabrication thanks to a simple structure, and light-weight/slim-dimension. Thus, the ELDs are widely applied to various fields such as a LCD backlight, mobile terminal, car navigation system (CNS), notebook computer, wall TV, and the like.
Such ELDs are divided into two categories, i.e. organic electroluminescent displays (hereinafter abbreviated OELDs) and inorganic electroluminescent displays (hereinafter abbreviated IELDs) in accordance with materials used for luminescent layers, respectively. IELDs, which emit light using the collisions of electrons accelerated by an high electric field, are classified into AC thin film ELDs, AC thick film ELDs, DC thick film ELDs, and the like in accordance with the film thickness and driving systems. And, OELDs, which emit light by a current flow, are classified into low-molecular OELDs and high-molecular OELDs in accordance with organic materials used for luminescent layers, and the low-molecular OELDs are classified into low-molecular fluorescent OELDs and low-molecular phosphorescent OELDs.
Meanwhile, in order that electrical displays attain high quality such as high-resolution, high-brightness, large-size, and the like, required are active type electrical displays having a switching device in each of pixels. Among various types of switching devices, amorphous silicon or poly-silicon thin film transistors are mainly used for the active type electrical displays. However, the amorphous silicon or poly-silicon thin film transistors have demerits such as a complicated fabrication process and high manufacturing cost. Particularly, in the case of OELDs driven in a current mode, since active type OELDs require more than two thin film transistors as well as more than one capacitor, the structure and fabrication process are complicated. Moreover, since the active type OELDs require high-level fabrication technologies, it is difficult to achieve a high production yield, and the manufacturing cost is high.
FIG. 1 illustrates a schematic bird's-eye view of disassembled upper and lower plates of a plasma switched organic electroluminescent display (hereinafter abbreviated PSOELD) for pixel regions according to a related art. And, FIG. 2 schematically illustrates a cross-sectional view of the assembled upper and lower plates of the PSOELD shown in FIG. 1 along the bisecting lines A-A′ and B-B′, respectively, in which the upper plate (100) is rotated clockwise by 90 degrees with respect to the lower plate (200) for the convenience of understanding.
The PSOELDs consist of an upper plate (100) and a lower plate (200). The lower plate (200) includes a rear substrate (202), sustain electrodes (204), a dielectric layer (206), barrier ribs (208), and protective layers (210). The upper plate (100) confronting the lower plate (200) includes a front substrate (102), address electrodes (104), anode layers (106), insulating layers (108), electroluminescent layers (110), cathode layers (112), and exposed cathode electrodes (114). And, the cathode layers (112) are used as exposed anode electrodes with respect to the corresponding exposed cathode electrodes (114).
On the rear substrate (202) confronting the front substrate (102), a plurality of the sustain electrodes (204) are formed in parallel with each other like stripes. In this case, every two adjacent sustain electrodes construct a plurality of sustain electrode pairs. One electrode of the sustain electrode pair is separated from the other electrode at an interval of several tens to several hundreds of micrometers and the sustain electrodes (204) are several hundreds of micrometers wide. The dielectric layer (206) restricting a discharge current is formed on the rear substrate (202) including the sustain electrodes (204) at a thickness of several to several tens of micrometers.
A plurality of the barrier ribs (208) are formed on the dielectric layer (206) at a height of several hundreds of micrometers so as to define plasma discharge spaces and prevent a plasma discharge from diffusing into other adjacent cells. In this case, the barrier ribs (208) are formed to provide a lattice structure including a plurality of lattices so that a pair of the sustain electrodes (204) constructing the sustain electrode pair can be placed in specific ones of the corresponding plasma discharge spaces in the same row or column of the lattice structure. And, a plurality of the protective layers (210) are formed at a thickness of sub-micrometer to several micrometers on the exposed surface of the dielectric layer (206) between the barrier ribs (208) by vacuum evaporation using MgO or the like having a high secondary electron emission coefficient to protect the dielectric layer (206) from plasma etching as well as make a plasma discharge occur with ease.
On the front substrate (102) of the upper plate (100), a plurality of the address electrodes (104) and exposed cathode electrodes (114) are formed alternately in parallel with each other like stripes crossing the sustain electrodes (204) of the lower plate (200) at right angles. A plurality of the anode layers (106) are formed like stripes between and in parallel with the address electrodes (104) and exposed cathode electrodes (114) on the front substrate (102), using a transparent conductive material such as ITO (indium tin oxide), IZO (indium zinc oxide), or the like.
In order to increase a contrast ratio by cutting off light from a plasma discharge, a plurality of the insulating layers (108) made of a black insulating material are formed on the front substrate (102) including the address electrodes (104), exposed cathode electrodes (114), and anode layers (106). And, a plurality of through-hole type anode contact holes (116) exposing portions of the anode layers (106) are formed by removing the insulating layers (108) located on the anode layers (106) and exposed cathode electrodes (114).
A plurality of the electroluminescent layers (110) are formed on the insulating layers (108) including the anode contact holes (116). In this case, each of the electroluminescent layers (110) is formed in rectangular shape enough to cover the corresponding anode contact hole (116). And, a plurality of the cathode layers (112) made of a conductive metal such as aluminum or the like are formed on the electroluminescent layers (110) by vacuum evaporation. In this case, the electroluminescent layers (110) are selected from the group consisting of high-molecular organic electroluminescent materials, low-molecular fluorescent organic electroluminescent materials, low-molecular phosphorescent organic electroluminescent materials, and the like.
The upper and lower plates (100) and (200) are aligned, making each of the anode contact holes (116) placed between the corresponding barrier ribs (208) as well as confront the corresponding sustain electrode pair (204). A mixed gas of Ne—Xe or Ne—Xe—Ar is injected into the respective plasma discharge spaces between the barrier ribs (208) at pressures below one atmosphere, thereby enabling to generate plasmas. For instance, a mixed gas of Ne(96%)-Xe(4%) is injected at 500 torr to generate plasmas. When the electroluminescent layers (110) are formed of low-molecular phosphorescent organic electroluminescent materials, the electroluminescent layers (110) are deposited by thermal evaporation using a shadow mask. Both hole injection layers (118) and hole transport layers (120) are further inserted between the anode layers (106) and electroluminescent layers (110). The hole injection layers (118) are formed on the anode layers (106), and the hole transport layers (120) are formed between the hole injection layers (118) and electroluminescent layers (110). And, both hole blocking layers (122) and electron transport layers (124) are further inserted between the electroluminescent layers (110) and cathode layers (112). The hole blocking layers (122) is formed on the electroluminescent layers (110), and the electron transport layers (124) are formed between the hole blocking layers (122) and cathode layers (112).
Unfortunately, the plasma switched organic electroluminescent display according to the related art has the following drawbacks. Because the cathode layers (112), which act as exposed anode electrodes with respect to the exposed cathode electrodes (114), have larger areas exposed to plasmas than the exposed cathode electrodes (114), the amount of electric current becomes small; thus, the operation voltage rises, and the power consumption increases. The maximum electric current capacity is decreased as well. Moreover, owing to the exposed cathode electrodes (114), the areas of the organic electroluminescent devices are decreased structurally, and the aperture ratio is subsequently decreased.